Optical spectroscopy technology has been widely used to detect and quantify the characteristics or concentration of a physical, chemical or biological target object. Optical diagnostics using this optical spectroscopy allows for the ability to obtain chemical and biological information without taking a physical specimen or the ability to obtain information in a non-destructive method with a physical specimen. The challenge is that the adoption of this technology has been limited due to the size of equipment and its cost. Therefore, its application was historically limited to centralized labs with scaled testing protocols. The opportunity now exists to develop a compact and low cost spectrometer. Among those previous efforts to miniaturize the spectrometer to expand the application of this optical spectroscopy into broader uses, the planar waveguide-based, grating-based, and Fabry-Perot-based techniques have been the major approaches. Recently there also have been efforts to miniaturize the spectrometer into chip scale using plasmonic nano-optic methods.
One of the issues encountered when trying to miniaturize the spectrometer is the resolution degradation. The resolution is usually dominated by the optics, especially by the distance from the input slit where the input light comes into the system to the detector array (or PDA, photo diode array). The shorter the distances, are the higher the resolution degradation. In case of non-dispersion methods or spectrum sensor using sets of filters, the number of the filters and shape or bandwidth (FWHM: Full Width Half Maximum) of each filter dominate the degradation. The more number of filters and the narrower FWHM provides the higher resolution.